10. The command 'sudo /etc/init.d/networking restart' returns:
Running etc/init.d/networking restart is deprecated because it may not enable again some interfaces.
* Reconfiguring network interfaces ...

Re: Atheros 242x/542x not connecting

OK, replacing the kernel seemed like a pretty drastic step, so I decided to experiment a little before going there (especially since chili555 said "There is nothing obviously wrong we can see to fix."). I downloaded the package 'wicd-gtk' and that program was able to initiate a connection to my router.

I should have mentioned earlier that I did not have a traditional desktop, but only the Openbox window manager. I'm used to relying on things like desktop widgets to connect to wireless networks automatically, so it didn't occur to me until recently that maybe I was missing a step in trying to establish a wireless connection. 'wicd-gtk' provided that missing step.

chili555, thanks so much for your help. I hope I haven't wasted too much of your time.